Graphitic Carbon Nitride Sensitized with CdS Quantum Dots for Visible-Light-Driven Photoelectrochemical Aptasensing of Tetracycline

Graphitic carbon nitride (g-C₃N₄) is a new type of metal-free semiconducting material with promising applications in photocatalytic and photoelectrochemical (PEC) devices. In the present work, g-C₃N₄ coupled with CdS quantum dots (QDs) was synthesized and served as highly efficient photoactive species in a PEC sensor. The surface morphological analysis showed that CdS QDs with a size of ca. 4 nm were grafted on the surface of g-C₃N₄ with closely contacted interfaces. The UV–visible diffuse reflection spectra (DRS) indicated that the absorption of g-C₃N₄ in the visible region was enhanced by CdS QDs. As a result, g-C₃N₄–CdS nanocomposites demonstrated higher PEC activity as compared with either pristine g-C₃N₄ or CdS QDs. When g-C₃N₄–CdS nanocomposites were utilized as transducer and tetracycline (TET)-binding aptamer was immobilized as biorecognition element, a visible light-driven PEC aptasensing platform for TET determination was readily fabricated. The sensor showed a linear PEC response to TET in the concentration range from 10 to 250 nM with a detection limit (3S/N) of 5.3 nM. Thus, g-C₃N₄ sensitized with CdS QDs was successfully demonstrated as useful photoactive nanomaterials for developing a highly sensitive and selective PEC aptasensor

Redox Potentials and Electronic States of Iron Porphyrin IX Adsorbed on Single Crystal Gold Electrode Surfaces

Metalloporphyrins are active sites in metalloproteins and synthetic catalysts. They have also been studied extensively by electrochemistry as well as being prominent targets in electrochemical scanning tunneling microscopy (STM). Previous studies of FePPIX adsorbed on graphite and alkylthiol modified Au electrodes showed a pair of reversible Fe­(III/II)­PPIX peaks at about −0.41 V (vs NHE) at high solution pH. We recently used iron protoporphyrin IX (FePPIX) as an intercalating probe for long-range electrochemical electron transfer through a G-quadruplex oligonucleotide (DNAzyme); this study disclosed two, rather than a single pair of voltammetric peaks with a new and dominating peak, shifted 200 mV positive relative to the ≈−0.4 V peak. Prompted by this unexpected observation, we report here a study of the voltammetry of FePPIX itself on single-crystal Au(111), (100), and (110) and polycrystalline Au electrode surfaces. In all cases the dominating pair of new Fe­(III/II)­PPIX redox peaks, shifted positively by more than 200 mV compared to those of previous studies appeared. This observation is supported by density functional theory (DFT) which shows that strong dispersion forces in the FePPIX/Au electronic interaction drive the midpoint potential toward positive values. The FePPIX spin states depend on interaction with the Au(111) interface, converting all the Fe­(II)/(III)­PPIX species into low-spin states. These results support electrochemical evidence for the nature of the electronic coupling between FePPIX and Au-surfaces, and the electronic states of adsorbate molecules, with a bearing also on recent reports of magnetic FePPIX/Au­(111) interactions in ultrahigh vacuum (UHV)

A Cathodic “Signal-off” Photoelectrochemical Aptasensor for Ultrasensitive and Selective Detection of Oxytetracycline

A novel cathodic “signal-off” strategy was proposed for photoelectrochemical (PEC) aptasensing of oxytetracycline (OTC). The PEC sensor was constructed by employing a p-type semiconductor BiOI doped with graphene (G) as photoactive species and OTC-binding aptamer as a recognition element. The morphological structure and crystalline phases of obtained BiOI-G nanocomposites were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The UV–visible absorption spectroscopic analysis indicated that doping of BiOI with graphene improved the absorption of materials in the visible light region. Moreover, graphene could facilitate the electron transfer of BiOI modified electrode. As a result, the cathodic photocurrent response of BiOI under visible light irradiation was significantly promoted when a suitable amount of graphene was doped. When amine-functionalized OTC-binding aptamer was immobilized on the BiOI-G modified electrode, a cathodic PEC aptasensor was fabricated, which exhibited a declined photocurrent response to OTC. Under the optimized conditions, the photocurrent response of aptamer/BiOI-G/FTO was linearly proportional to the concentration of OTC ranging from 4.0 to 150 nM, with a detection limit (3<i>S</i>/<i>N</i>) of 0.9 nM. This novel PEC sensing strategy demonstrated an ultrasensitive method for OTC detection with high selectivity and good stability

Vpliv športnorekreativne vadbe na gibljivost in moč gibalno oviranega otroka

Among the low-index single-crystal gold surfaces, the Au(110) surface is the most active toward molecular adsorption and the one with fewest electrochemical adsorption data reported. Cyclic voltammetry (CV), electrochemically controlled scanning tunneling microscopy (EC-STM), and density functional theory (DFT) calculations have been employed in the present study to address the adsorption of the four nucleobases adenine (A), cytosine (C), guanine (G), and thymine (T), on the Au(110)-electrode surface. Au(110) undergoes reconstruction to the (1 × 3) surface in electrochemical environment, accompanied by a pair of strong voltammetry peaks in the double-layer region in acid solutions. Adsorption of the DNA bases gives featureless voltammograms with lower double-layer capacitance, suggesting that all the bases are chemisorbed on the Au(110) surface. Further investigation of the surface structures of the adlayers of the four DNA bases by EC-STM disclosed lifting of the Au(110) reconstruction, specific molecular packing in dense monolayers, and pH dependence of the A and G adsorption. DFT computations based on a cluster model for the Au(110) surface were performed to investigate the adsorption energy and geometry of the DNA bases in different adsorbate orientations. The optimized geometry is further used to compute models for STM images which are compared with the recorded STM images. This has provided insight into the physical nature of the adsorption. The specific orientations of A, C, G, and T on Au(110) and the nature of the physical adsorbate/surface interaction based on the combination of the experimental and theoretical studies are proposed, and differences from nucleobase adsorption on Au(111)- and Au(100)-electrode surfaces are discussed

Highly Selective Self-Powered Sensing Platform for <i>p</i>‑Nitrophenol Detection Constructed with a Photocathode-Based Photocatalytic Fuel Cell

A photocathode-based photocatalytic fuel cell (PFC) was fabricated and proposed as a self-powered sensor for <i>p</i>-nitrophenol (<i>p</i>-NP) detection. The PFC was comprised of a photocathode and an anode in separated chambers, which could generate suitable power output under photoirradiation to drive the sensing process. In this device, p-type PbS quantum dots-modified glass carbon electrode (GCE) served as the photocathode for the reduction of <i>p</i>-NP under photoirradiation while graphene-modified GCE was employed as the anode for the oxidation of ascorbic acid. In order to improve the selectivity of the PFC sensor, <i>p</i>-NP binding molecularly imprinted polymer (MIP) was introduced on the photocathode. Under optimal conditions, the open circuit voltage of the constructed PFC sensor was found to sensitively respond to <i>p</i>-NP in a wide concentration range from 0.05 μM to 20 μM. The proposed sensor exhibited high selectivity, good reproducibility, and stability, demonstrating the successful combination of MIP with photocathode in construction of high-performance PFC self-powered sensors for pollutant monitoring

Site-specific risk assessment and integrated management decision-making: A case study of a typical heavy metal contaminated site, Middle China

<p>A typical contaminated land was spatially investigated and assessed based on Chinese guidelines to establish remediation strategy for exploring the shortcomings of the current guidelines to suggest improvements. Results showed that Cr, As, Pb, and Cd should be regarded as the priority pollutants under sensitive land use, while Cr and As should be regarded as the priority pollutants under insensitive land use. Ingestion of soil for each studied metal appeared to be the main exposure pathway under both the land uses. The calculated screening values of the priority metals were conservative to certain extent—even some were lower than their background values. Therefore, an integrated risk management strategy was suggested and the hierarchic clean-up values were proposed considering the health risk, local background value, land remediation cases, current remediation technology, and financial cost. Consequently, it was suggested the clean-up values of Cr(VI), Cr, As, Pb, and Cd, under future sensitive land use, should be 7.5, 1000, 30, 250, and 1.4 mg/kg in the first class control layer, respectively. For future insensitive land use, the clean-up values of Cr(VI), Cr, As, Pb, and Cd should be 20.4, 8000, 60, 580, and 4.3 mg/kg in the first class control layer, respectively.</p

Phase III Trials of Standard Chemotherapy with or without Bevacizumab for Ovarian Cancer: A Meta-Analysis

<div><p>Background</p><p>Platinum-based standard chemotherapy improves survival of ovarian cancer (OC), but the five-year survival rate remains below 50%. Antiangiogenic agents (7.5 or 15 mg/kg Bevacizumab, Bev) plus to standard chemotherapy improve progression-free survival (PFS) not overall survival (OS) in completed randomized controlled trials (RCTs). The efficacy and safety of two doses of Bev + standard chemotherapy remain controversial.</p> <p>Methods</p><p>MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane databases and <a href="http://clinicaltrials.gov" target="_blank">ClinicalTrials.gov</a> were searched. The outcomes of eligible RCTs included PFS, OS and toxicities. Hazard ratio (HR) and relative risk (RR) were used for the meta-analysis and were expressed with 95% confidence intervals (CIs).</p> <p>Results</p><p>Bev + chemotherapy improved PFS (HR, 0.82; 95% CI, 0.75 to 0.89; <i>P</i> = .000) and OS (HR, 0.87; 95% CI, 0.77 to 0.99; <i>P</i> = .026) in newly diagnosed OC (2 trials, 2776 patients), and PFS (HR, 0.48; 95% CI, 0.41 to 0.57; <i>P</i> = .000) in recurrent OC (2 trials, 845 patients). Bev + chemotherapy increased non-CNS bleeding (RR, 3.63; 95% CI, 1.81 to 7.29; <i>P</i> = .000), hypertension grade ≥ 2 (RR, 4.90; 95% CI, 3.83 to 6.25; <i>P</i> = .000), arterial thromboembolism (RR, 2.29; 95% CI, 1.33 to 3.94; <i>P</i> = .003), gastrointestinal perforation (RR, 2.90; 95% CI, 1.44 to 5.82; <i>P</i> = .003), and proteinuria grade ≥ 3 (RR, 6.63; 95% CI 3.17 to 13.88; <i>P</i> = .000). No difference was observed between the two Bev doses in PFS (HR, 1.04; 95% CI, 0.88 to 1.24) or OS (HR, 1.15, 95% CI, 0.88 to 1.50), but 15 mg/kg Bev increased toxicities.</p> <p>Conclusion</p><p>Bev + standard chemotherapy delayed progression for newly diagnosed and recurrent OC, and improved survival for newly diagnosed OC. The 7.5 mg/kg dose appeared to be optimal for newly diagnosed OC patients with high risk for progression.</p> </div

Comparison of the efficacy and safety of two dose of Bev.

<p>(A) progression-free survival curves; (B) overall survival curves; and (C) toxicity incidence between 7.5 mg/kg and 15 mg/kg Bev. Black <i>P</i>: toxicity incidence between ICON7 and GOG-0218 control arms; red <i>P</i>: toxicity incidence between 7.5 mg/kg and 15 mg/kg bevacizumab + standard chemotherapy arms. ATE: arterial thromboembolism; Bev: bevacizumab; CNS: central nervous system; HR: hazard ratio; GIP: gastrointestinal perforation; OS: overall survival; PFS: progression-free survival; VTE: venous thromboembolism.</p

Photoelectrochemical Aptasensing of Kanamycin Using Visible Light-Activated Carbon Nitride and Graphene Oxide Nanocomposites

Photoactive material and recognition element are two crucial factors which determine the sensitivity and selectivity of the photoelectrochemical (PEC) sensor. Herein we developed a novel PEC aptamer sensor for the specific detection of kanamycin using water-dispersible graphite-like carbon nitride (w-<i>g</i>-C₃N₄) as visible light-active material and aptamer as the biorecognition element. While a suitable amount of graphene oxide (GO) was doped in w-<i>g</i>-C₃N₄, the visible light photocurrent response was enhanced, which was beneficial to the construction of PEC sensor. On the other hand, the large specific surface area and π-conjugated structure of GO/w-<i>g</i>-C₃N₄ provided an excellent platform for immobilizing the kanamycin-binding DNA aptamer on the surface of the sensor via π–π stacking interaction. On such a sensor, the capture of kanamycin molecules by aptamer resulted in increased photocurrent. The PEC response of the sensor was found to be linearly proportional to the concentration of kanamycin in the range from 1 nM to 230 nM with a detection limit (3S/N) of 0.2 nM. Moreover, the proposed sensor displayed high selectivity, good reproducibility, and high stability, demonstrating the successful combination of GO/w-<i>g</i>-C₃N₄ with aptamer in fabricating high performance PEC sensors

Progression-free survival by baseline risk factor.

<p>Bev: bevacizumab; chemo: chemotherapy; FIGO: International Federation of Gynecology and Obstetrics; HR: hazard ratio.</p